1. Field of the Invention
This invention relates to electroactive fluorene copolymers. The invention further relates to electronic devices in which the active layer includes such polymeric materials.
2. Description of the Related Art
Organic electronic devices such as devices that emit light, such as light-emitting diodes that make up displays, are present in many different kinds of electronic equipment. In all such devices, a photoactive layer is sandwiched between two electrical contact layers. At least one of the electrical contact layers is light-transmitting so that light can pass through the electrical contact layer. The photoactive layer emits light through the light-transmitting electrical contact layer upon application of electricity across the electrical contact layers.
It is well known to use organic electroluminescent compounds as the active component in light-emitting diodes. Simple organic molecules such as anthracene, thiadiazole derivatives, and coumarin derivatives are known to show electroluminescence. Several classes of luminescent polymers have also been disclosed. These include, for example, poly(1,4-phenylene vinylene) and derivatives; polythiophenes, especially, poly(3-alkylthiophenes); and poly(p-phenylenes). Alkyl and dialkyl derivatives of polyfluorene have also been disclosed, as in U.S. Pat. Nos. 5,708,130 and 5,900,327.
There is a continuing need for photoactive compounds having improved efficiency and processes for preparing them.